This invention relates generally to a method for media blasting and finishing a gear or other workpiece or part and cleaning the workpiece thereafter. The powered part hold-down apparatus of U.S. Pat. No. 5,272,897 may be used for the peening step(s) of the present disclosure, and the disclosure of the U.S. Pat. No. 5,272,897 is hereby incorporated in its entirety by this reference. Elements of other known methods of media blasting and finishing, such as the peen finishing method and apparatus of U.S. Pat. No. 8,453,305, may be used for the present disclosure, and the disclosure of the U.S. Pat. No. 8,453,305 is hereby incorporated in its entirety by this reference.
Media blasting or peening is used to increase the fatigue strength of a gear, workpiece or part. Gears, such as those utilized in automobile transmissions are media blasted to increase their surface durability and ensure that they are suitable for performing their intended functions. As an example, media blasting with steel peening may be used for strengthening the root radius of the teeth of a geared workpiece. The media blasting steps of the present invention includes the steps disclosed in U.S. Pat. No. 6,612,909 and the disclosure of the U.S. Pat. No. 6,612,909 is hereby incorporated in its entirety by reference.
When media blasting a workpiece, such as a gear, the workpiece is placed in a closed chamber and the blasting system is actuated, whereby media are mixed with air. After mixing of the media and air, a stream of the air/media mixture is directed against the workpiece, often through increased or high-speed application. This process is referred to as peening. The peening process is configured to affect and change the characteristics of the surface of the workpiece, and in particular increase the strength of the workpiece. Accordingly, media blasting a workpiece improves the durability of a workpiece.
Due to the force/speed of the peening process, as well as the size and characteristics of the peening media, peening material or particles of peening material that have broken off from peening material may be retained or lodged on the surface of the workpiece after the peening process has occurred. This may be especially true for gears or other workpieces that have teeth or grooves, as the peening material may be retained within recesses or grooves of the workpiece. Alternatively or additionally, particles from the part being processed by break off and be retained or lodged on the surface of the workpiece. Such particles may be very small or microscopic in size, depending on the original size of the media, the force at which the media is blasted, the hardness of the surface of the workpiece, etc. A variety of materials/media may be used for media blasting the workpiece, depending on the ultimate application or outcome desired by the workpiece.
In automotive applications, it is often desired to increase the strength or hardness of the surface of the workpiece in order to have more favorable KSI. In the present disclosure toughness is discussed in terms of “KSI” (kilo-pound[-force] per square inch) or 1000 psi. KSI is often used in materials science, civil and mechanical engineering to specify stress and Young's modulus. A higher KSI is favorable for materials that will be under larger compressive stresses. When a workpiece, in particular a workpiece made of media that has a high KSI, is peened, the peening material is blasted against the surface of the workpiece, removing and modifying the microscopic landscape of the surface. Due to the nature of the peening process, material that has been removed or blasted from the surface of the workpiece may be retained on the workpiece after the peening process has occurred.
It is advantageous to have a workpiece with a smooth surface without particles, media, or debris on or lodged into the surface when a workpiece or part is utilized in its final application/configuration. Accordingly, it is known to clean the workpiece after a peening process, for example, through a spray and wash unit. However, given the microscopic size of the particles, the force at which the peening material is blasted, and the shape and size of the workpieces being processed, traditional forms and processes of cleaning may not remove all particles or material from the surface of the workpiece.
This background information is provided to offer some information believed by the applicant to be of possible relevance to the present disclosure. No admission is intended, nor should such admission be inferred or construed, that any of the preceding information constitutes prior art against the present disclosure. Other aims, objects, advantages and features of the disclosure will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.